1. Field of the Invention
The present invention concerns a component for a magnetic resonance system, as well as a magnetic resonance system, as well as a method for manufacturing the component, wherein susceptibility artifacts in a resulting magnetic resonance image are reduced.
2. Description of the Prior Art
In magnetic resonance (MR) measurements (data acquisitions), the homogeneity of the static, multi-Tesla basic magnetic field (referred to as the BO field) is decisive. Inhomogeneities in the magnetic field can be caused not only by the presence of metallic structures in or in the vicinity of the basic magnetic field, but also by plastic components, insofar as such plastic components have a relative permeability that deviates from 1. This deviation is known as the susceptibility μr=Xv+1. Such susceptibility artifacts become noticeable in anatomical MR images as errors in the spatial resolution. In functional magnetic resonance imaging (fMRI) it is necessary to superimpose an anatomical image of the subject and an fMRI image. The fMRI image is obtained by providing a sensory stimulus (sight, sound or touch) to the subject and detecting the change in blood oxygen level in the brain that occurs following the stimulus. By identifying the location or locations of such increased oxygen saturation in the brain with respect to an anatomical image of the patient's brain, the localized area within the brain in which the sensory activity occurs can be identified, and conclusions can be made as to whether this brain activity is normal or pathological. Since the change in blood oxygen level resulting from such sensory activity is extremely small, this type of magnetic resonance data acquisition is particularly sensitive to susceptibility artifacts.
In order to permit the most desirable conditions to be present in the magnetic resonance system during the acquisition of magnetic resonance data in an fMRI procedure, it is conventional to obtain the necessary anatomical image in a separate procedure that is conducted before the fMRI procedure. Typically this anatomical image is acquired by computed tomography, with the necessity of administering a relatively large quantity of contrast agent to the patient. Moreover, it is also typical to acquire this anatomical image several days before the fMRI procedure, and therefore difficulties may exist in precisely superimposing the anatomical image and the fMRI image. During the actual fMRI procedure, it is typical to make use of conventional two-dimensional digital radiography images, also requiring the administration of contrast agent, in order to monitor the procedure. Another option is to make use of trans-esophageal ultrasound (TEE).
In procedures of the type described above, as well as for other magnetic resonance data acquisition procedures, it is known to fabricate components of the magnetic resonance system from plastic in an effort to minimize the occurrence of such susceptibility artifacts. As noted above, however, even plastic material does not have a permeability that is precisely equal to 1, which is the so-called permeability of free space. As also noted above, it is this deviation from pre-space permeability that is the fundamental cause of susceptibility artifacts.
Moreover, plastic components in a magnetic resonance system must exhibit a variety of other properties in addition to a low magnetic susceptibility, and these other properties, such as insensitivity to flexural fatigue stress, biocompatibility, elasticity, appearance, workability, long-term stability, and insensitivity to environmental influences, often compete with each other as well as competing with the desire for low magnetic susceptibility.